Jeff Davis <[EMAIL PROTECTED]> writes: > On Fri, 2007-06-08 at 12:22 -0400, Tom Lane wrote: >> Now that I'm awake, it is reachable code, per this comment: >> >> * Note: when we fall off the end of the scan in either direction, we >> * reset rs_inited. This means that a further request with the same >> * scan direction will restart the scan, which is a bit odd, but a
> I'm confused about this part of the comment. If you tell the SeqScan plan node to fetch forward over and over, it eventually will return NULL indicating end-of-data. If you then demand *another* forward fetch, it'll start the whole scan over from scratch, because of the fact that it sees rs_inited clear. You might've expected another NULL but that's not what you'll get. In general, however, the behavior of a plan node in this scenario is not defined and not relied on by anything --- some of the join node types will crash outright if you try to fetch past EOF, IIRC. The case that *is* required is to be able to scan backwards after returning NULL. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 7: You can help support the PostgreSQL project by donating at http://www.postgresql.org/about/donate